I. Field of the Invention
The present invention relates to a method for manufacturing a display device with a plurality of light-emitting diodes (LEDs) and, more particularly, to a method for manufacturing a display device by an improved resin molding method.
II. Description of the Prior Art
Generally, in a display device for displaying numbers and figures with a plurality of light-emitting diodes arrayed on an insulating substrate, the display device is provided with a light-transmitting insulating resin layer for improving the external luminous efficacy of the LEDs and for protecting the LEDs. The resin layer is formed by molding which is a significant technique in the manufacture of the display device.
As shown in FIG. 1, in conventional resin molding, a plurality of LEDs 2 are adhered by a silver paste to an insulating substrate 1 on which a wiring layer and terminals are formed. Wire bonding (not shown) is then performed. An adhesive tape 5 is adhered to the outer surface of the bottom of a synthetic resin case or frame 3 which has a wall and a through hole for housing each one of the LEDs 2. A predetermined amount of an insulating resin 4 is filled into the case 3. The surface of the insulating substrate 1 on which the LEDs 2 are formed faces downward and the insulating substrate 1 is inserted in the case 3. The insulating resin is thermally set to form an integral body of the case 3 and the insulating substrate 1. The adhesive tape 5 is peeled off from the bottom to prepare a display device.
However, according to the above conventional method for manufacturing a display device, the following problems are presented:
(1) Air bubbles tend to be trapped in the insulating resin 4. A defoaming process is required to eliminate the air bubbles. However, the air bubbles cannot easily be eliminated completely. Displayed objects become unclear due to the presence of air bubbles.
(2) The amount of insulating resin 4 to be filled into the case must be properly controlled, and accurate alignment of the case 3 with the insulating substrate 1 is required.
(3) The wall in the case 3 which is filled with the insulating resin 4 is necessary to manufacture the display device. However, if display devices of this type are assembled to form a large display device, the outermost LEDs of each display are spaced apart from each other due to the presence of the walls 3a. Thus continuity of the displayed figure cannot be achieved.